1. Field of the Invention
The present invention relates to a method for manufacturing a display panel. More specifically, the present invention relates to a technique for making a flat display panel typical of a liquid crystal display using a glass substrate thinner and lightweight.
2. Description of the Related Art
Recently, with an increase in the demand for a display panel such as a liquid crystal display in a mobile application, there has been a growing need to make the display panel thinner and lightweight. A glass substrate takes up large amounts of thickness and weight in the display panel. To make the display panel thinner and lightweight, the glass substrate must be thin. When focusing on a large liquid crystal display, the thickness of the glass substrate has been reduced from 1.1 mm to 0.7 mm in recent years. In this case, the thickness of the glass substrate has been simply reduced to be introduced into the assembling process, so that the production line has not been required to be changed largely. It is considered that the thickness of 0.7 mm can correspond to a display panel having a diagonal substrate size of up to 1 m.
However, the need for making the substrate thinner is increased in the mobile application. The substrate thickness in the next stage is assumed to be 0.5 mm. When the thickness of the glass substrate is reduced to 0.5 mm, the deformation is increased. For example, considering the glass substrate having a size of 600 mmxc3x97700 mm, the thickness cannot correspond to the current production and carrying techniques. For this reason, it is considered that when the size of the substrate is reduced to 400 mmxc3x97500 mm so as to restructure the production line. However, when the size of the substrate is reduced, the number of liquid crystal panels as final products obtained for each substrate, thereby lowering the productivity greatly. In addition, there is an attempt to make the display panel thinner by assembling a thick substrate into the display panel so as to mechanically polish the surface of the glass substrate. In the mechanical polishing method, however, after the large substrate is assembled so as to be cut out to a plurality of panels, the individual panels are subject to mechanical polishing, thereby lowering the productivity. As described above, when attempting to introduce the thin substrate in the beginning of the production line, the substrate size cannot be increased without limitation due to the influence of the deformation of the substrate. When attempting to make the substrate assembled into the panel thinner by polishing, the panels are removed from the substrate one by one, and then, are polished. Long time is then required so as to lower the productivity.
In view of the foregoing problems of the prior art, an object of the present invention is to provide a producing method for realizing the weight and thickness reduction of a display panel without reducing the substrate size and lowering the productivity. To achieve such an object, the following measures are taken. A method for manufacturing a display panel according to the present invention comprises a panel producing step for manufacturing a display panel using substrates each having a predetermined wall thickness; and a chemical treatment step for immersing the display panel into a chemical solution and removing a fixed amount of the surface of the substrates by a chemical reaction so as to reduce the wall thickness. Preferably, in the chemical treatment step, the temperature change of the chemical solution is controlled so as to be within the range from a predetermined temperature to xc2x15xc2x0 C., thereby removing a fixed amount of the surface of the substrates. In this case, in the chemical treatment step, a predetermined temperature of the chemical solution is between 30xc2x0 C. and 60xc2x0 C. In the chemical treatment step, the concentration change of the chemical solution is controlled so as to be within the range from a predetermined concentration to xc2x15 wt %, thereby removing a fixed amount of the surface of the substrates. In this case, in the chemical treatment step, a predetermined concentration of the chemical solution is between 10 wt % and 30 wt %. In the chemical treatment step, a substance precipitated by the chemical reaction is recovered from the chemical solution, thereby removing a fixed amount of the surface of the substrates. In the chemical treatment step, the display panel is immersed into the chemical solution while circulating the chemical solution filled in a vessel, thereby removing a fixed amount of the surface of the substrates. In the chemical treatment step, the display panel is immersed into the chemical solution while introducing bubbles into the chemical solution for stirring, thereby removing a fixed amount of the surface of the substrates. In the chemical treatment step, the display panel is immersed into the chemical solution while swinging, thereby removing a fixed amount of the surface of the substrates. Between the panel producing step and the chemical treatment step, a foreign particle removing step for removing foreign particles deposited onto the substrates is performed. In this case, in the foreign particle removing step, ozone water is exerted on the substrates to remove foreign particles. After the chemical treatment step, pure water heated to 40xc2x0 C. or higher is used to perform a chemical solution removing step for removing the chemical solution deposited onto the substrates. The chemical treatment step includes a procedure for detecting whether a fixed amount of the surface of the substrates is removed or not. In the chemical treatment step, the substrates made of glass are immersed into a chemical solution containing hydrofluoric acid and sulfuric acid, thereby removing a fixed amount of the surface thereof. In the panel producing step, a display panel is produced by superposing two substrates each having a predetermined wall thickness together by a predetermined gap, and after the chemical treatment step, a liquid crystal implanting step for implanting liquid crystals into the gap of the display panel is performed. Otherwise, in the panel producing step, a display panel is produced by forming an electroluminescence element on one substrate having a predetermined wall thickness, and in the chemical treatment step, the display panel is immersed into the chemical solution while the electroluminescence element is protected, thereby removing a fixed amount of the surface of the substrate.
According to the present invention, for example, after two substrates constructing a display panel are combined with each other, these substrates are immersed into a chemical solution, thereby removing a fixed amount of the surface of the substrates surface by a chemical reaction. Since the individual display panels are processed together before being cut out from a large substrate, the productivity cannot be lowered. In the assembling stage, since a thick substrate is used to advance the producing process, any handling problem will not arise when the substrate is increased. Since the thickness of the substrate is reduced constantly over the entire surface, the temperature of the chemical solution for use in the chemical reaction is adjusted within xc2x15xc2x0 C. in the present invention. In the similar object, the variation of the concentration of the chemical solution is adjusted within the range of xc2x15 wt %. Since re-deposition of the substance generated during the chemical reaction interferes with uniform removal of the wall thickness, a measure for preventing the re-deposition is taken. For example, during immersion of the substrate, a filter is used to recover the substance precipitated by the chemical reaction. The chemical solution is circulated during the treatment. A gas is mixed into the chemical solution so that the bubbling acts on the substrate. In addition, during the treatment, the substrate being immersed can be swung. To perform the chemical treatment uniformly, between the step for superposing the substrates together and the step for chemically etching the substrate, a step for removing foreign particles deposited onto the substrate is added. In the foreign particle removing step, organic foreign particles are removed using, for example, highly oxidative ozone water. In a rinsing step for removing the chemical solution deposited onto the substrate, hot pure water at 40xc2x0 C. or higher is used as a rinsing liquid to facilitate drying. During or after immersion of the substrate, removal of a predetermined amount is monitored to quantitatively control the thickness of the substrate.
In the method for manufacturing a display panel according to the present invention, the surface of a substrate is subject to a semiconductor process to form a pixel array, and then, the substrate superposed together with other substrate or a protective member is immersed into a chemical solution to etch the surface of the substrates by a chemical reaction. The semiconductor process can be performed to the surface of the thick substrates. A chemical reaction process is simply added to the current display panel producing process so as to obtain a thin and lightweight display panel. In the producing method according to the present invention, the panel is immersed into a chemical solution so as to remove a fixed amount of the surface of the substrates by a chemical solution. The substrates can be batch-processed. For this reason, a chemical solution tank is increased, 20 large substrates of about 600 mmxc3x97700 mm can be processed per hour. There is adaptability as mass production equipment.